Shielded electrical conductor



Feb. 19, 1957 R. c. woor-'TER SHIELDED ELECTRICAL CCNDUCTOR Filed DeC. 13, 195] ZM ma T v .N a, Nw a, a. am Nm, Q 7 l U Q .M lill I l|| l E W w.. Il I l m H I! e@ Tl I @w HTTOZN YS United States Patent O SHIELDED ELECTRICAL CONDUCTOR Robert C. Woofter, Cortland, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 13, 1951, Serial No. 261,431

2 Claims. (Cl. 174-77) This invention relates to electrical conductor assemblies, particularly such assemblies as are provided with radio shielded connecting elements and especially to assemblies of this type which are adapted to be used as connections to the spark plugs of internal combustion engines, but it will be understood that the connector assemblies which are the subject of the invention are not limited to this particular use.v

it is desirable that conductor assemblies of this type be waterproof, highly flexible and inexpensive. Shielded connector assemblies disclosed in the prior art have had so little ilexibility that it has been found necessary to provide elbows connected to the ends of the conductor assembly in order to utilize lsuch conductor in certain installations, and such assemblies, which are waterproof, are sutciently expensive for cost to be a serious consideration.

lt is accordingly a primary object of the present invention to devise a conductor assembly of the type referred to which is highly exible, is completely water proof and is relatively inexpensive and to devise a suitable method of making such a conductor.

According to the present invention, the conducting element, itself, which is surrounded by suitable insulating material and connected at its ends topsuitable terminal connections, extends through a metallic conduit which is non-waterproof, and is of the ordinary well known interlock type which is inexpensive and readily flexible. This is surrounded by a shielding covering formed'of copper wire braid soldered to flanged ferrules which are engaged by connecting nuts which are adapted to secure the conductorvin position when installed, in the usual manner. The braid is surrounded by a relatively thin protective neoprene sheath and this sheath extends into the ferrules which are so tightly crimped around the sheath that the conductor is rendered waterproof.

In making the conductor assembly the protective sheath is extruded on the braid as a continuous process so that the conductor with the neoprene sheath applied thereto is formed in bulk by a continuous operation and is cut into whatever lengths are desired for any particular installation before the ferrules are connected thereto` Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

The ligure is an elevation, partly in section, of the two ends of a conductor constructed in accordance with the present invention.

The conductor comprises a wire or conducting element 2 which is surrounded by a layer of suitable insulation 4 and has resilient terminals 6. Each terminal is a wire in the form of a helix that extends beyond the end of the wire 2. The manner of connecting the terminal to the wire 2 forms no part of the present invention but, as disclosed, the insulating material 4 is surrounded g 2,782,250 Patented Feb. 19, 1957 at one end by an insulating sleeve 8 of some suitable ceramic material and this sleeve has an internal ange 10 which engages a metallic sleeve 12 of brass or some other suitable material, between two flanges, 14 and 16, formed on sleeve 12 and the terminal wire 6 is also connected to the sleeve between the flanges 14 and 16. The conducting element 2 extends through the sleeve 12 and is connected to the sleeve by means of a brass nail 18 which is driven into the wire 2 as shownin the drawings, clamping the wire between itself and the sleeve.

The conducting element 2, with its insulation 4, is surrounded by a metal conduit 20 which is spaced from the insulating material 4 as shown in the drawing, and this conduit is formed of a spiral strip which surrounds the insulating material and has interlocking edges, which are shown in section at 21 on the drawing. A conduit i of this character is well known, is commonly used to surround electrical wiring and is relatively inexpensive and quite ilexible, so that the assembled conductor can be readily bent and can be used in many installations without connecting elbows, where elbows would be required with connectors of the prior art.

Surrounding the conduit 20 is a metallic shielding covering one or more layers 22 formed of braided copper wire, two layers being shown herein covering 22 fitting tightly around the conduit 20. The shielding covering is connected at each end to a ferrule 24 by means ot solder indicated at 26 so that such covering is mechanically and electrically connected to the ferrules. Surrounding the insulated conductor 2 is a sleeve 28 of rubber, neoprene or otherA suitable flexible insulating material which is of sufficient thickness to fit tightly between the insulation 4 and the inner surface of the conduit 20. The sleeve 28 is provided with a ange 30 and extending from the flange 30 is a cup-shaped projection 32 which ts around the ceramic sleeve 8 when the conductor is assembled. Engaging the lange 3i) is a collar 34 which isengaged by a spring 36, the other end of whichy engages another collar 38 which is positioned between the spring 36 and the end of the ferrule 24. The purpose of this spring will be'described more fully later.

Surrounding the shielding covering 22 is a protective sheath of neoprene or other suitable material 40 which, in forming the conductor assembly, is extruded on the outer surface of the shielding covering 22 as the latter is moved continuously through a suitable extruding die so. that the sheath is applied to the shielding covering 22 by a continuous process and the conductor 'assemblyy is continuously formed in bulk. For any particular installation, the conductor assembly thus formed is cut into pieces of whatever length is necessary before the ferrules or the terminals are connected thereto. When the ferrules are attached, a water-tight joint is formed between the ferrules and the protective sheath 40.

As will be apparent from the drawing, the ferrule 24 is formed with a skirt 42 having a wall thickness somewhat less than that part of the ferrule adjacent the flange 43 and as the ferrule is originally formed, this skirt is slightly ared so that the Vferrule can be readily positioned upon the outer surface of the sheath 40 which projects into the ferrule for a distance about equal to the length of the flared skirt so that the end of the sheath is ad* jacent the shoulder 4S on the inside of the ferrule. When the sheath and the ferrule are assembled in the relation shown, the ferrule is crimped or swaged upon the sheath 40 with suiicient force to cause the ferrule to grip the sheath tightly enough to form a water-tight joint.

It will be noted that the ferrule 24 is provided with a flange 44 which is adapted to be engaged by a cooperating nut 46. This nut is internally threaded and when the conductor is assembled with a spark plug or with some other terminal to which it is adapted to supply electric current, the nut is screwed on the spark plug or some other element to hold the conductorv in operative position. When the nut is tightened, the spring 36 is cornpressed so as to hold the terminal 6 against its cooperating terminal with sufficient force to establish a good contact and to hold the ange, 30 of sleeve 28 against a cooperating part, when the conductor assembly is aS- sembled in operative position, with sufficient force to form a water tight seal.

The specific construction of the terminals is no part of the present invention and the conductor could be used with other suitable terminals.

` It will be understood that the application of the pro tective sheath to the outer surface of the shielding covering by extrusion, is a matter of much importance. 4In conductor assemblies of this type disclosed in the prior art there are, some which have ferrules quite similar to the ferrules 24 and a protective sheath corresponding to the sheath 4t?. However, in such conductor assemblies, the sheath does not extend into the ferrules but merely abuts the end of such ferrnle so that the waterproofing must be effected by other means and the protective sheath is molded on the shielding covering so that different molds are required for different length conductor assemblies, thus greatly increasing the manufacturing cost.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An electrical conductor assembly for use with the surrounding said llexible metal conduit, a resilient terminal connected to said conducting element, a protective sheath of flexible waterproof material surrounding and applied to the outer surface of said shielding covering means for connecting the conductor assembly in operative position including a ferrule positioned adjacent the end of the conductor assembly, said ferrule having an annular ange portion and a part surrounding said protective sheath and engaging the sheath with sulilcient force to form a water-tight joint between itself and said sheath, a cooperating nut engaging the annular ange portion of said ferrule and adapted to hold the conductor in operative position, a flange member mounted on the conducting element adjacent the terminal, resilient means between said flange member and the flange portion of said ferrule, adapted to exert pressure between said flange 4 member and the flange portion of said ferrule engaged by said nut when the conductor is assembled in position, in order to exert a pressure on the terminal through the ange member to insure a good contact and a watertight seal at the flange member.

2. An electrical conductor assembly for use with the spark plugs of an internal combustion engine or the like having in combination a conducting element surrounded by a sheath of suitable insulating material, a flexible metal Conduit surrounding said sheath, a shielding covering surrounding said flexible metal conduit, a resilient terminal connected to said conducting element, a protective sheath of exible water-proof material surrounding and. applied to the outer surface of said shielding covering, means for connecting the conductor assembly in operative position including a ferrule positioned adjacent the end of the conductor assembly, said ferrule having an annular flange portion and a skirt portion, an internal shoulder formed with the skirt portion dividing the skirt portion into parts of which the wall thickness adjacent the flange portion of said ferrule is slightly greater than the wall thickness of the remainder of the skirt portion, said shielding covering being mechanically and electrically connected to said ferrule adjacent said flange portion by means of solder with the greater wall thickness part of said skirt portion engaging said shielding covering, said protective sheath being assembled in tightly pressed engagement with the thinner wall thickness part of said skirt portion adjacent said shoulder with sufficient force to form a water-tight joint therebetween, a cooperating nut engaging the annular flange portion of said ferrule and adapted to hold the conductor in operative position, a flange member mounted on the conducting element adjacent the terminal, and a coil spring between said flange member and the flange portion of said ferrule, one end of the spring exerting pressure on said ferrule and the other end exerting pressure on said flange member when the conductor is assembled in position by said nut in order to exert a pressure on the terminal through the flange member resulting in a resilient sealing contact of a water-tight nature at the ange member.

References Cited in the tile of this patent UNITED STATES PATENTS 1,227,726 Woodhead May 29, 1917 1,509,224 Berthold Sept, 23, 1924 1,930,639 Berthold n-.. n Oct. 17, 1933 2,134,946 Hurley Nov. 1, 1938 2,402,050 Ingalls June 11, 1946 2,577,049 Uline Dec. 4, 1951 

